The experimental tools employed in these experiments include separation of lymphocytes into subpopulations by taking advantage of specific cell surface receptors and erythrocyte rosette techniques. Cell subpopulations are further purified by complement mediated lysis of human T-lymphocyte antigen or B-lymphocyte antigen positive cells. Purified T-lymphocyte subpopulations are then reconstituted with autologous freshly infected B-lymphocytes and within days, the pattern of B-cell outgrowth is observed: inhibited, enhanced, or not affected at all. The proposed experiments will confirm and extend our understanding of the events which occur during outgrowth inhibition of lymphocytes freshly infected in vitro with EBV and co-cultivated with IgG-Fc receptor positive T-lymphocytes (TG cells). Through experiments with donors from newborn to old age, the ontogeny including the age of decline, of TG cell mediated inhibition will be investigated and specific efforts will be directed toward inducing the inhibitory cell in neonatal lymphocyte subpopulations. Finally, we seek to understand the mechanism which results in enhanced outgroth of infected lymphocytes cultured in conditioned medium. Because these experiments utilize freshly infected lymphocytes before they are changed by viral replication and/or cell transformation, they closely mimic events which occur in vivo when virus spreads from cell to cell as transformed cells emerge. The experiments may yield important information about the mechanisms involved in transformed cell surveillance.